Solvent-resistant polybenzimidazole-based anion exchange membranes without crosslinkers for stable mono-valent/di-valent anion separation

The discharge of industrial wastewater containing organic solvents and mixed inorganic ions causes severe resource waste and poses significant risks to environmental sustainability and human health. To address the challenge of recovering resources (e.g., salts) from complex wastewater systems, electrodialysis (ED) using ion exchange membranes （IEMs） with robust thermal, mechanical, and chemical stability has emerged as a promising strategy. In this study, a series of polybenzimidazole (PBI)-based anion exchange membranes (AEMs) functionalized with dual-side-chains have been developed, exhibiting a low swelling ratio (<10 %), exceptional solvent resistance, and high perm-selectivity for Cl − /SO₄ 2− separation during ED. The optimized PBI-IM-6C membrane demonstrates outstanding stability, with a weight loss of <6 % after 120-day immersion in various organic solvents at room temperature and no detectable degradation after one week in DMAc at 80 °C. Notably, the PBI-IM-6C membrane could achieve a Cl − /SO₄ 2− perm-selectivity of 49.11 (vs. 6.50 for Neosepta ACS) at 2.5 mA·cm −2 , along with long-term stability in organic solvent-containing systems. Furthermore, the effects of current density (2.5/5 mA·cm −2 ), feed concentration (0.05/0.1 M), and ternary ion competition (Cl − /SO₄ 2− /NO₃ − ) on separation performance were systematically investigated. This work highlights the potential of crosslinker-free AEMs for efficient mono-valent/di-valent anion separation in organic solvent-mediated ED processes, offering a sustainable approach to wastewater treatment and resource recovery.